This type of tire is expected to be used for cars which run freely at substantially high speeds on a paved road, an unpaved road, a wet road, or an icy road or the like. Important performances for the purposes as described above are cornering performance, shock-absorbing performance, friction performance, and performance of running with low noises or the like. It is important for obtaining these performances that each of the tires should contact the road with a large ground contact area, namely, at a comparatively low ground pressure. Also, in a case where a car runs on a snowy road surface or an icy road surface, the tires, especially during driving, are slippery, so that the air pressure of the tires is lowered to make the ground contact area larger, ordinary types of tire are changed to so-called spike tires, or the tires are covered with chains for driving thereon.
Conventional types of tires have difficulties keeping their desired ground contact area, even if a driver wants to reduce the air pressure of each tire to make the ground contact area thereof larger, the air pressure of the tire cannot excessively be reduced and there are some limits in reducing the air pressure in each tire because the air pressure is one of the most important elements for maintaining the form and functions of the tire. The spiked tire and the use of chain are attended with troubles such as dust or the like produced in the case where a car with spiked tires or with tires covered with chains runs on an ordinary road other than a snowy road surface or an icy road surface and, in addition, it is troublesome to change the tires or to attach and detach the chains thereto and therefrom.